Tag: homo erectus

In October 2013, Lordkipanidze and his colleagues reported the discovery of an adult skull from Dmanisi, Georgia. The fifth skull to be discovered at the site, it was complete and undeformed; it is the only known fully-preserved adult hominin skull from the early Pleistocene. They also put forward the radical suggestion that the various species often proposed for early African Homo (Homo habilis, Homo rudolfensis, Homo ergaster and Homo erectus) were all actually variants of the same species, and that early Homo was a single lineage which evolved over time without differentiating into multiple species. This conclusion is based on a claim that shape variation between the five Dmanisi skulls is roughly the same as that seen among the various early Homo skulls from East Africa, even though the former represents a single species and the latter are generally thought to represent several (Lordkipanidze, et al., 2013).

This suggestion must now be reconsidered in the light of last week’s announcement that the LD 50-1 partial lower jawbone places the origins of Homo at least 2.8 million years ago (Villmoare, et al., 2015); and Spoor and colleagues’ reappraisal of the OH 7 Homo habilis type specimen. The latter report that firstly, the cranial capacity of OH 7 is estimated at between 729 and 824 cc, which is substantially larger than 500 to 700 cc typically cited and within the range of early Homo erectus; and secondly, OH 7 is more primitive than the 2.33-million-year-old AL 666-1 upper jawbone provisionally assigned to Homo habilis, despite being 500,000 years younger.

Spoor and colleagues suggest that AL 666-1 cannot be placed within either Homo habilis or Homo rudolfensis. They do not investigate its true affinities further but suggest that their data is consistent with it belonging to Homo erectus. That it is more derived than Homo habilis implies that the origins of the latter must be sought even further back in time than 2.33 million years ago. The reporting that LD 50-1 is transitional between Australopithecus and Homo places the origin of the latter at around 2.8 million years ago. Putting the two reports together, the implication is that Homo was already diverse lineage by 2.33 million years ago, and that early human types were distinguished by facial morphology rather than by brain size.

Lordkipanidze and his colleagues noted that the morphological diversity within the five skulls recovered at Dmanisi is greater than that recorded for specimens recovered in Africa and assigned to different species. On the basis that the Dmanisi hominins all belong to the same species, they suggest that the morphological diversity in African fossil record of Homo 1.8 million years ago is better interpreted as demes of a single evolving lineage of Homo erectus rather than multiple species.

Given that Homo habilis, Homo rudolfensis and Homo erectus might all have emerged by 2.33 million years ago, an ancestor/descendant relationship between these species seems unlikely. It could be argued that the deme interpretation is more parsimonious than the traditional multiple species view.

Against this view, it has been suggested that the limb proportions of Homo habilis are more apelike (longer arms, shorter legs) than those of Homo erectus (Richmond, et al., 2002). The main problem is that in comparison to classic fossils such as ‘Lucy’ (Australopithecus afarensis) and the Turkana Boy (Homo erectus), we do not have a well-preserved example of Homo habilis. The evidence for the apelike limb proportions of Homo habilis largely rests on the two fragmentary skeletons KNM-ER 3735 and OH 62.

In the case of OH 62, the leg is represented by an upper section of the femur, the true length of which is uncertain. KNM-ER 3735 preserves even less limb detail. A re-evaluation of these specimens in comparison to fossil limb parts OH 34 and OH 35 suggests that the upper-to-lower limb ratio of OH 62 lies within the upper range of modern humans and lower range of chimpanzees; and that KNM-ER 3735 lies in the middle of the modern range, entirely outside the chimpanzee range. Based on these results, the limb proportions of Homo habilis were modern rather than apelike (Haeusler & McHenry, 2004).

Overall, these results appear to refute suggestions that Homo habilis should be reclassified as an australopithecine (Wood & Collard, 1999) and are consistent with the conclusions of Lordkipanidze and his colleagues.

Could partial lower jawbone be from a Denisovan – or an entirely new species?

A partial fossil human jawbone from Taiwan is reportedly the first archaic hominin to be found there. The jawbone was dredged by a fishing net from the 60 to 120 m (200 to 400 ft.) deep Penghu Channel, 25 km (15.5 miles) of the island’s western coast. Also recovered were vertebrate fossils known as the terminal Middle/Late Pleistocene ‘Penghu fauna’. Both Taiwan and the Penghu Channel were part of the Asian mainland during Pleistocene episodes of lowered sea levels. The jawbone found its way to an antique shop in Tainan City, where it was purchased by a local man who in turn donated it to the National Museum of Natural Science of Taiwan.

The nature of its recovery means that there is no stratigraphic data by which the Penghu 1 jawbone can be dated. Accordingly, researchers measured its fluorine and sodium content in relation to that of other Penghu fossils. Fluorine, deriving from the surroundings, tends to accumulate slowly over time in buried bones; sodium on the other hand exists at about one percent in the bones of living vertebrates, but decreases when they are fossilised. By this means, the researchers matched Penghu 1 with fossil remains of Crocuta crocuta ultima, an extinct Eurasian subspecies of the spotted hyena that reached northern China between 500,000 and 250,000 years ago, but did not reach southern China until 240,000 years ago. There were episodes of lowered sea levels between 190,000 to 130,000 years ago and from 70,000 to 10,000 years ago; Penghu 1 probably dates to one of these two intervals.

Penghu 1 is identified as archaic by its relatively large molars and premolars, and by its lack of a chin. The short and relatively wide shape of its dental arcade is derived in comparison to the earliest humans (Homo habilis and the Dmanisi hominins), but other than that it cannot readily be assigned to any particular archaic human species. The second molar is larger than those of other archaic Asian hominins, and the low, thick body is closer to some examples African and European Homo from 400,000 years ago than to Early/Middle Pleistocene Asian Homo, with the exception of the 400,000-year-old Chinese Hexian Homo erectus remains.

The large second molar suggests Denisovan affinities in M2 crown size, but unfortunately no Denisovan lower jawbones or lower M2 teeth have yet been found for comparison. Not until we have a Denisovan lower jawbone that can be identified as such by genetic means will we have a better idea if Penghu 1 belonged to a Denisovan. Nor can we rule out the possibility that Penghu 1 represents a completely new archaic human species.

Archaeologists studying freshwater mussel shells excavated in the nineteenth century at Trinil, Java, have discovered geometric patterns carved by Homo erectus 500,000 years ago and unambiguous evidence that one shell had been sharpened and polished for use as a cutting tool. In addition, the number of large adults in the shell assemblage suggests that they were intentionally collected for eating.

The shells were excavated by Dutch anthropologist Eugene Dubois in 1891 during the course of his work in Java, which led to the discovery of Homo erectus. They now form part of the Dubois Collection in the Naturalis Biodiversity Centre in Leiden. Researchers dated sediments within the shells with argon-argon and luminescence methods to obtain an age range of 540,000 to 430,000 years old.

The engraved shell, designated DUB1006-fL, displays a geometric pattern of grooves. The pattern consists of a zigzag line with three sharp turns producing an ‘M’ shape, a set of more superficial parallel lines, and a zigzag with two turns producing an inverted ‘N’ shape. The grooves appear to have been intentionally produced, and comparison with experimentally-made grooves suggest that they were made with a shark tooth.

Previously, the earliest evidence for the carving of abstract patterns was the engraved ochres from Blombos Cave, South Africa, which date from the period 100,000 to 75,000 years ago, and the 60,000 year old engraved ostrich shells from Diepkloof Cave, South Africa. Neanderthals made abstract rock engravings at Gorham’s Cave, Gibraltar, 39,000 years ago. More controversially, it has been suggested that a 230,000 year old pebble found at Berekhat Ram in the Golan Heights is a representation of the female form.

The cutting tool is the earliest-known example of the use of shells for tool-making, and may have been a response to the lack of locally-available material for making stone tools. A similar explanation has been proposed for Neanderthal shell tools from Italy and Greece, but these are only around 110,000 years old.

Finally, seafood is a dietary adaptation was once thought to be exclusive to modern humans, beginning around 165,000 years ago. Subsequently it was discovered that Neanderthals were exploiting seafood on the Malaga coast 150,000 years ago. The Trinil shells show that the use of seafood by humans was a much earlier development.

Overall, the Trinil shells suggest that Homo erectus possessed a far greater behavioural flexibility than previously believed in terms of both tool-making technology and subsistence strategies. The engraved geometric pattern suggest that at least some capacity for symbolic thought was already present in early humans 500,000 years ago.

The findings are published in the journal Nature.

Reference:

1.Joordens, J. et al., Homo erectus at Trinil on Java used shells for tool production and engraving. Nature (2014).

Human footprints up to one million years old discovered at Happisburgh, Norfolk

Footprints left by small group of adults and children are oldest discovered outside Africa

Human footprints dating to between one million and 780,000 years old have been reported on the beach of the coastal village of Happisburgh, Norfolk (pronounced ‘Hazeborough’), and are the earliest-known direct evidence for the presence of humans in northern Europe. The footprints briefly emerged at low tide in May 2013, having being exposed by rough seas.

Within a fortnight, they had vanished again – but not before a team led by Nick Ashton from the British Museum had obtained plaster casts and 3d images. A total of 152 footprints were recorded, of which twelve yielded complete outlines suitable for analysis. It is thought that these twelve footprints represented five individuals ranging in height from 0.93 to 1.73 m (3 ft. 0 in. to 5 ft. 8 in.), suggesting the presence of both adults and children. It has been suggested that the Happisburgh hominins are related to Homo antecessor (‘Pioneer man’), a human species known from Sierra de Atapuerca in northern Spain during the period between 1.2 million and 800,000 years ago (Ashton, et al., 2014).

Early humans from this period are broadly categorised as Homo erectus. In Europe, Homo erectus was later replaced by the larger-brained Homo heidelbergensis, which might have been the forerunner of the Neanderthals in Europe and modern humans in Africa.

The Happisburgh footprints are the earliest direct evidence for humans in Britain, but tools used by these first Britons have been coming to light since 2005, when 700,000-year-old flint artefacts were reported from Pakefield in Suffolk (Parfitt, et al., 2005). In 2010 even earlier flint artefacts were reported from Happisburgh, estimated to be at least 780,000 years old, and probably older (Parfitt, et al., 2010). Previously, the earliest uncontested evidence for humans in northern Europe dated to no earlier than around 500,000 years ago (Parfitt, et al., 2005).

Analysis of animal remains suggests the Happisburgh people occupied the edges of forests at what was then an estuary of the River Thames, and lived towards the end of a warm interglacial period. It is not certain when the interglacial occurred, but there were warm periods from 866,000 to 814,000 years ago, and from 970,000 to 936,000 years ago (Parfitt, et al., 2010).

Britain was at this time connected to the mainland and lying on the southern edge of the forests of northwestern Europe. The climate was similar to that of today and while comfortable by British standards, it would have been chilly for those used to a Mediterranean or African climates. It remains unclear whether expansion into northern latitudes with lower winter temperatures required human physical adaptation, seasonal migration or developments in technology such as hunting, clothing, the use of shelters and the control of fire (Parfitt, et al., 2005; Parfitt, et al., 2010; Roberts & Grun, 2010).

Did ‘hobbit people’ of Flores evolve from Homo erectus or a more primitive hominin?

Homo floresiensis is an extinct Late Pleistocene hominin species known only from the Indonesian island of Flores. The type specimen LB 1 is a diminutive 30-year-old female who stood just 1.06 m (3 ft. 6 in.) tall. Nicknamed ‘Flo’, she had a cranial capacity initially estimated to be just 380 cc, comparable to that of an australopithecine. Her weight was estimated to be somewhere between 16 and 36 kg (35 and 79 lb.). Yet she was apparently human: she lacked the large back teeth of an australopithecine, the proportions of her facial skeleton were those of a human, and she appeared to be a humanlike fully-committed biped (Brown, et al., 2004; Morwood, et al., 2004).

The extremely small cranial capacity has been hotly debated since the species was first described in 2004. Some have claimed that Flo was a modern human suffering from microcephaly, a developmental disorder leading to a smaller brain (Jacob, et al., 2006; Martin, et al., 2006), but the majority reject this view and recognise Homo floresiensis as a new human species with a long, low cranial vault and other features characteristic of archaic humans (Argue, et al., 2006; Falk, et al., 2005; Falk, et al., 2007; Tocheri, et al., 2007; Lyras, et al., 2008).

Two principle theories have emerged as to the origin of these hominins. The first is that Homo floresiensis was a dwarf form of Homo erectus (approximate cranial capacity 1,000 cc) which underwent a dramatic reduction in size as a result of a phenomenon known as insular dwarfism. Animals living on an island where food is relatively scarce and predators are few or absent will ‘downsize’ over many generations, in order to reduce calorific requirements. What is actually happening is that evolution is favouring the smaller offspring in each generation. If predators do not pose a threat, any advantages in being large will be outweighed by poorer fuel-economy. What has to be questioned is whether insular dwarfism could lead to brain size reduction of the extent seen in Homo floresiensis.

The second theory is that Homo floresiensis is derived from a hominin species more primitive and smaller-brained than Homo erectus such as Homo habilis (approximate cranial capacity 600 cc) or even an australopithecine (approximate cranial capacity 400 cc). This second model implies that Homo erectus was not the first hominin species to leave Africa, contrary to the widely-accepted Out of Africa 1 hypothesis.

Two studies, one published in 2010 and the other earlier this year, have focussed on decreases in brain size. The first study considered the decreases in body mass and brain size that have been documented for a number of other primate lineages. Researchers tested putative ancestors for Homo floresiensis against these, using the high, medium and low estimates of its body mass. Results suggested that Homo erectus is only feasible as an ancestor for Homo floresiensis if the low estimate of 16 kg (35 lb.) is accepted. For the medium estimate of 24 kg (53 lb.), Homo habilis or the Dmanisi hominins are more feasible as ancestors. The high estimate is not compatible with any proposed scenario (Montgomery, et al., 2010).

The second study re-evaluated the brain size of Homo floresiensis using micro-CT scanning, and obtained an upwardly-revised estimate of 425 cc. This revised figure means that the degree of brain size reduction in relation to body mass is less, and therefore easier to explain. Nevertheless, if Homo erectus was the ancestor, the decrease in brain size is still too great to be explicable solely as a scaling downwards as body mass is downsized, and some other factor must have come into play. In an environment where food is scarce, and given that brain tissue is ‘expensive’ in metabolic terms, further reduction in brain size might have been advantageous. However, this could not be achieved without some loss of cognitive ability. The authors of the report suggested that cognitive abilities comparable to Homo habilis might have sufficed in an island habitat lacking dangerous predators (Kubo, et al., 2013).

While this ‘dumbing down’ scenario cannot be dismissed, it seems implausible. According to the widely-accepted ‘social brain hypothesis’ (Byrne & Whiten, 1988), the large primates of primates evolved in response to a need to predict the likely future social behaviour of their fellows, and base relationships upon these predictions. While Homo floresiensis would not have had to face dangerous predators, individuals would still need to interact with other group members. It is difficult to see that being less smart than one’s fellows could be anything over than a severe disadvantage, regardless of other circumstances.

I would therefore be inclined to the view that Homo erectus was not the ancestor of Homo floresiensis, and this view is supported by a number of studies considering the skeletal evidence. These have noted that while the cranial metrics were consistent with Homo erectus, the limb proportions of Homo floresiensis had more in common with Australopithecus garhi (Argue, et al., 2006) and the feet were a mosaic of primitive apelike and derived humanlike features. The big toe was fully in-line, albeit short, and the metatarsals followed a humanlike sequence in which the 1st (innermost) was the most robust (sturdily-built), followed by the 5th (outermost), then 4th, 3rd, and finally 2nd. The foot, though, was disproportionately long in comparison to that of a modern human; the lesser metatarsals (2nd to 5th) were long; and the outer toes were long and curved, unlike the short, straight toes of a modern human (Jungers, et al., 2009). The fact that the feet and limb proportions of Homo erectus were modern suggests that Homo floresiensis evolved from a species that was more primitive, such as Homo habilis.

References:

1.Brown, P. et al., A new small-bodied hominin from the Late Pleistocene of Flores, Indonesia. Nature431, 1055-1061 (2004).

2.Morwood, M. et al., Archaeology and age of a new hominin from Flores in eastern Indonesia. Nature431, 1087-1091 (2004).

Java Man is the popular name given to the fossil hominin discovered in 1891 by Eugene Dubois at the village of Trinil, on the banks of the Solo River in eastern Java. The find consisted of a skullcap and a femur. It is uncertain if are from the same individual and the femur is believed by some to be from a modern human. Dubois initially named his find Anthropithecus erectus (“Upright man-ape”, suggesting it was more ape-like than human) then he renamed it Pithecanthropus erectus (“Upright ape-man”, suggesting closer human affinities).

Peking Man is the popular name given to the fossil hominins discovered in the 1920s and 1930s at Zhoukoudian, near Beijing and described as Sinanthropus pekinensis by Davidson Black.

In 1944 both species were reclassified as Homo erectus by the late Ernst Mayr as part of a general tidying-up exercise of the bewildering plethora of hominin genera and species then recognised.

Eugene Dubois (1858-1940) was a Dutch anatomist who became fascinated with the subject of human origins. He had been an avid fossil-collector from childhood and believed that fossils provided the best way of elucidating evolutionary history, an approach which was not universally accepted at the time.

Dubois became convinced that the best place to search for the fossil origins of mankind would be the tropics, and to this end he joined the Dutch army as a doctor and had himself posted to the Dutch East Indies, arriving in Sumatra in December 1887. The demands of his day job meant it was quite a while before he could begin his search of the many caves in Sumatra, where he believed the fossil evidence would be found. Eventually, though, he was able to investigate the caves at Lida Adjer and duly began to unearth the bones of various mammals. Armed with this evidence, he managed to persuade the Dutch government to relieve him of his medical duties and allow him work full time on his fossil-hunting. He was also assigned the services of fifty convicts to help him with his excavations.

After failing to discover any human fossils in Sumatra, Dubois received permission in April 1890 to transfer his work to neighbouring Java. He began searching cave sites, but again without success, so he began investigating open sites as well. Finally he was rewarded with success and in October 1891, at Trinil, he recovered a low-domed angular thick-walled human skullcap with a large shelf-like brow ridge. In August 1892 he recovered a humanlike femur from what he believed to be the same site.

Convinced he had found the “missing link” – a transitional form between humans and apes, Dubois at first proposed the name Anthropithecus erectus based on what he believed were the ape-like proportions of its brain – which he estimated at 700cc – and the modernity of the femur. However in November 1892 he revised the cranial capacity upwards to 900cc, closer to that of a modern human than an ape. Accordingly he renamed the fossil Pithecanthropus erectus.

In 1895 Dubois returned to Europe and embarked on a tour to promote his claim to have found the missing link. Although the scientific community were intrigued by his discoveries, his conclusions were generally rejected. Disappointed, he eventually accepted a position as professor of geology at the University of Amsterdam and refused to allow any examination of his fossils until, under increasing pressure to grant access, he finally relented in 1923. His motives have been questioned: the popular view is that he was acting out of spite, like an angry schoolboy taking his ball and going home. However it is more likely that he was protecting his intellectual property. In 1897 he had permitted Gustav Schwalbe of the University of Strasburg to make a cast of the skullcap: Schwalbe had then produced a monograph that had been far more sympathetically received than any of Dubois’ own work.

By the 1920s and 1930s further hominin fossils were coming to light. In 1927 the Canadian anthropologist Davidson Black described Sinanthropus pekinensis (“Chinese man of Peking” [Beijing]), based on an examination of two teeth recovered from the cave site of Zhoukoudian in Dragon Bone Hill, near Beijing. The find became popularly known as Peking Man. Several skullcaps were recovered from the same site in subsequent years. Both Black and anatomist Franz Weidenreich noted similarities between the Zhoukoudian finds and Pithanthropus, but Dubois rejected the similarities.

Unfortunately the Zhoukoudian fossils were lost during World War II. Work at the site was halted by the Japanese invasion in 1937, but the fossils remained at the Cenozoic Research Laboratory of the Peking Union Medical College until 1941, when an attempt was made to transfer them to the United States for safekeeping. They were never seen again. It is thought that they were in possession of a group of US marines, who were captured when war broke out between Japan and the USA. Fortunately Weidenreich had made plaster casts, now in the American Museum of Natural History, New York. After the war, excavation resumed at Zhoukoudian and a number of discoveries have been made since, including two skull fragments. Zhoukoudian became a World Heritage site in 1987.

In 1936 palaeontologist Ralph von Koenigswald made a further discovery on Java itself. Excavating near Mojokerto, eastern Java, in 1936, von Koenigswald recovered a juvenile skull now known as the Mojokerto Child, who was anything from 2 to 6 years old at death, but again Dubois rejected any affinities to Pithecanthropus. The following year, von Koenigswald made further discoveries at Sangiran, East-Central Java with the aid of local people, who he promised to pay 10 cents for each find. The finds included fragments making up an almost-complete skull, though von Koenigswald’s delight at this discovery was somewhat tempered when he learned his helpers were breaking larger finds into smaller pieces to maximise their bounty!

Dubois argued his find was more ape-like than the later discoveries, leading to the popular misconception that he had repudiated his claim that it was an intermediate form. Eugene Dubois died in December 1940, having done himself few favours in the last four decades of his life. British anthropologist Sir Arthur Keith, writing in an obituary notice, observed that Dubois was “an idealist who held his ideas so firmly that he tended to bend the facts rather than alter his ideas to fit them.”

It is now generally accepted that the Javanese and Chinese hominins belong to the same or closely-related species, usually classed as Homo erectus. Some authorities recognise a separate species, Homo pekinensis, for the Chinese hominins.

Dating the Javanese fossils using modern argon-40/argon-39 and potassium/argon dating techniques of volcanic material recovered from the same context as the fossils has been problematic. This is due to deformation and distortion by earth movements of the stratigraphic beds with which the fossils are associated. Another problem has been uncertainty regarding the exact discovery sites, which were less scrupulously recorded than would now be the case. Dates ranging from as recent as 1.0 million to as long ago as 1.65 million have been proposed. Dates of 1.81 million years for the Mojokarto Child and 1.66 million years for the Sangiran fossil were reported in 1994 (Swisher et al, 1994).

Homo erectus (or pekinensis) fossils from Zhoukoudian and elsewhere in China have been dated to between 800,000 and 400,000 years old by palaeomagnetic and biostratigraphic techniques. However stone tools from the Nihewan Basin, 150km (90 miles) west of Beijing have been dated to as far back as 1.6 million years old, implying a much earlier arrival.

Homo georgicus is the name proposed to describe fossil human remains that have been found at the medieval town of Dmanisi, Georgia from 1991. The site has been of interest to archaeologists for many years and bones of extinct mammals had previously been recovered from the site. Mode I stone tools, similar to the Oldowan tradition of East Africa, and comprising flakes and flaked pebbles were discovered in 1984. The human remains include four partial human skulls and two lower jaws.

A basalt layer below the fossils has been dated to between 1.95-1.77 million years old by magnetic polarity considerations, which are normal. The material occurring with the fossils shows reversed polarity, dating it from 1.77 million to 790,000 years. The mammal bones do suggest the earlier date based on when certain species overlapped in time.

The skull known as D2700 has an extremely small braincase volume of 600cc, similar to that of Homo habilis and it has been suggested that it has a closer relationship to this species than it does to African Homo ergaster or Asian Homo erectus. If so, it would imply that humans of the habilis rather than the erectus grade were the first to leave Africa. However a recent description of a metatarsal shows a close fit with the derived Homo ergaster body plan rather than that of Homo habilis, which retained many australopithecine features.